An example of a conventional stratified scavenging two-cycle engine is disclosed in Japanese Patent Laid-open No. 9-268917; and FIG. 12 herein shows a side sectional view of a stratified scavenging two-cycle engine 10 as described in the aforesaid Japanese Patent Laid-open. In FIG. 12, a muffler 80 is attached to an exhaust port 26, which is formed in a cylinder block 20 of the engine 10. Formed in an outer face of a crankcase 90, attached to the underside of the cylinder block 20, is a suction port 90a for sucking mixture into a crank chamber within the crankcase 90. A heat insulating pipe (suction pipe) 40 is connected to the suction port 90a, and a carburetor 60 is connected to the heat insulating pipe 40. An air control valve 50 is provided between the carburetor 60 and an air cleaner 70. The air control valve 50 is connected via an air supply pipe 55 to a scavenging port 20a, which is provided in the cylinder block 20. A check valve 20b is provided in the scavenging port 20a in the cylinder block 20. An ignition plug 30 is attached to the top of the cylinder block 20. A length, in a cross direction between an outer face of the air cleaner 70 and the outer face of the cylinder block 20 which is closest to the air cleaner 70, is set to be a dimension LA.
However, in the aforesaid art the air control valve 50 is provided between the carburetor 60 and the air cleaner 70. Therefore, the dimension LA, in a cross section between the outer face of the air cleaner 70 and the closest outer face of the cylinder block 20, is long, and the space required by the stratified scavenging two-cycle engine 10 is large. Consequently, there arises a disadvantage in that the workability of a shoulder hanging, hand-held, or knapsack-type mower for mowing grass, a chain saw, or the like, incorporating the engine 10 is inferior.
The distance from the air control valve 50 to the scavenging port 20a of the cylinder block 20 is long. Therefore, the air supply pipe 55 is made long, which results in a lack of compact disposition. In addition, there is a disadvantage in that the air supply pipe 55 is a hindrance to a workman because it can touch his body. There is another disadvantage in that the air control valve 50 and the carburetor 60 are manufactured separately, thus causing high manufacturing costs. Moreover, since the check valve 20b is provided within the cylinder block 20 in the engine assembly process, the productivity is low.